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Freeport-McMoRan Copper and Gold has ventured into the oil and natural gas space, following in the footsteps of fellow diversified miner BHP Billiton—and benefiting for the shift.

The mining industry has been struggling over the last year or so as supply has been greater than demand for most mined materials. That's why Freeport-McMoRan Copper and Gold(NYSE:FCX) has added oil and natural gas to the mix—just like BHP Billiton(NYSE:BHP). The companies, and their shareholders, are benefiting from the exposure.

Mining giantsFreeport-McMoRan Copper and Gold mines for its namesake copper and gold, as well as molybdenum and cobalt, with operations in the Americas, Africa, and Oceania. And, since acquiring Plains Exploration & Production Company and McMoRan in May and early June of this year, it is now involved in oil and natural gas drilling.

So far this strategic shift has been good news. For example, in the just ended third quarter, Freeport noted "Our third quarter results reflect strong operating performance from our global mining business together with an impressive and significant contribution from our recently acquired oil and gas operations."

"Impressive" and "significant" are strong words, but they fit. Although volume in copper and gold were up through the fist nine months of the year, Freeport's realized selling prices fell by 9% and 16%, respectively. And third quarter prices were weaker than the year-to-date figures, suggesting that prices are going the wrong way.

While year over year results aren't available for Freeport's oil and gas segment, the nine month period saw average prices of $79.40 for a barrel of oil equivalent. That figure in the third quarter stood at $80.93—Freeport's oil and gas business is seeing an improving price trend. That makes this new addition an island of strength in a generally weak industry.

Not aloneFreeport isn't alone in this shift. BHP Billiton provided a nice blueprint for success in rolling in oil and gas assets. For example, the company paid about $15 billion for Petrohawk Energy in 2011. At the time, the transaction jumped the company into the global top ten independent exploration and production companies.

In fiscal 2013, which ended in June, BHP Billiton's selling prices followed a similar downward path as Freeport's. Iron ore, copper, and coal, among others, were all weak. That led to a top line decline of about 9% and a bottom line drop of around 30%. Although oil prices were lower by 4%, following the broader trend to some degree, BHP's realized natural gas prices were up an impressive 17%. Diversification has its benefits.

The big boysWith a market cap of $38 billion, Freeport is a very large company. BHP, however, is even bigger, weighing in at over $190 billion. Although both pale in comparison to ExxonMobil(NYSE:XOM) at $400 billion, that shouldn't diminish their scale. For example, BHP is about the same size as Royal Dutch Shell(NYSE:RDS-B).

Although oil and gas aren't the sole focus at Freeport or BHP, the pair have the scale to be important industry participants. And that's good news for shareholders. More importantly, however, their diversified businesses provide noteworthy benefits that Royal Dutch Shell and ExxonMobil lack.

For example, Royal Dutch Shell took a swift one-day hit when it announced third quarter results partly because of production weakness. That compounds recent issues with finding new oil, including the very public grounding of a ship off Alaska. Shell will have big long-term problems if it can't replenish the only natural resource it's pulling out of the ground. Freeport-McMoRan Copper and Gold and BHP Billiton have years of reserves on the mining side and, with smaller oil and gas operations, should find it easier to support growth on that side of the business, too.

Striking a balanceWhile owning BHP or Freeport comes with its own set of risks, this pair's shift into oil and gas has been beneficial. And while they are suffering through weakness in core mining markets, the overall portfolio balance the pair provides, notably enhanced by oil and gas, makes these miners one-stop shops for natural resource exposure. Shell and Exxon, while both good companies, don't offer that.

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